From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 59C89D3A670 for ; Tue, 29 Oct 2024 17:18:55 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1t5pr5-0005iV-0z; Tue, 29 Oct 2024 13:18:07 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1t5pr3-0005iF-NE for qemu-devel@nongnu.org; Tue, 29 Oct 2024 13:18:06 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1t5pr1-0005rY-DX for qemu-devel@nongnu.org; Tue, 29 Oct 2024 13:18:05 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1730222281; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:in-reply-to:in-reply-to: references:references; bh=tCcjchzf9OKzkyqRhhA0g+uNjrR4Xxe1vbwj9HrUfKs=; b=RefJj1zoHZDAc2E+plVjpDRyt5XaUdDNm9HXmPaf6NC9zNtqEeIL/HCucJ3LLjTagYetAJ kWM81qse1X5/6AjLhGxQVOua9O+Ngh5mTe3X2U/4GqCvrBsOO4M+FBdcsBDv73+OyvXi7C KUxzZM23FyWFqwTZMkVdJDXHPlFL9iE= Received: from mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-355-qn_xi9gBM8iurkKSHUywaQ-1; Tue, 29 Oct 2024 13:17:58 -0400 X-MC-Unique: qn_xi9gBM8iurkKSHUywaQ-1 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 7EDBC19560A3; Tue, 29 Oct 2024 17:17:56 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.142]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 6D2BA1956056; Tue, 29 Oct 2024 17:17:50 +0000 (UTC) Date: Tue, 29 Oct 2024 17:17:47 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Peter Xu Cc: Markus Armbruster , qemu-devel@nongnu.org, Fabiano Rosas , Igor Mammedov , Juraj Marcin , "Michael S . Tsirkin" , "Dr . David Alan Gilbert" , =?utf-8?Q?C=C3=A9dric?= Le Goater , Eduardo Habkost , Alex Williamson , Paolo Bonzini , Peter Maydell Subject: Re: [PATCH 0/4] QOM: Singleton interface Message-ID: References: <20241024165627.1372621-1-peterx@redhat.com> <87h690my2w.fsf@pond.sub.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/2.2.12 (2023-09-09) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Received-SPF: pass client-ip=170.10.129.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -23 X-Spam_score: -2.4 X-Spam_bar: -- X-Spam_report: (-2.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.302, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Tue, Oct 29, 2024 at 01:05:04PM -0400, Peter Xu wrote: > But I'm not sure whether that's a concern at all for Libvirt, if what > Libvirt currently does is having separate "migrate-set-*" commands prior to > the "migrate". I may have overlooked the real issue behind on how that > could complicate Libvirt. > > > > > Rather than MigrationState become a singleton, I'd really encourage > > trying to see if we can fix the lifecycle design problems, so that > > we have a clear beginning & end of the migration operation, with the > > state discarded at the end, such that every future migrate starts > > from a clean base. > > I assume it implies the join() path as a start. As long as we're ok we > risk slow quits of QEMU, as I would expect bug reports coming afterwards, > we could try. I believe there's no way we can resolve all such issues in > one shot. I doubt whether some of those can be too tricky so we may wish > to go back at some point, spending too much effort but without a direct > benefit yet so far. > > Meanwhile we still have the immediate concern that current_migration can > points to freed memory right now with QEMU master branch. That's simply > wrong. Yeah, if we're accessing freed memory, that's a segv/abrt danger, and needs fixing quickly. With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|